The invention is based on a wiper blade for a window wiper, in particular a window wiper for a motor vehicle. The invention also relates to a method for producing such a wiper blade.
Wiper blades for window wipers are usually produced from elastomer materials. The use of elastomer materials on the one hand allows the wiper blades to adapt themselves to the contour of a windshield of a motor vehicle and on the other hand means that adequate elasticity is ensured under differing thermal requirements. In order that the window wiper leads to good wiping results in both directions of movement, a wiping rubber is usually produced from a base portion and a lip portion, wherein the base portion and the lip portion are connected to each other in such a way that the lip portion can flip over in accordance with the wiping direction of the window wiper. Usually, the base portion, the lip portion and the joint between the base portion and the lip portion are produced from the elastomer material as one part, for example by an extrusion process. In order to ensure sufficiently stable attachment of the lip portion and the base portion, however, a minimum thickness of the elastomer material in the joint region is required. This may, however, lead to a restriction of the swiveling movement. Moreover, the elastomer material in the joint region is subjected to additional loading by the regular flipping over, which can lead to a weakening of the material.
In order to strengthen the base portion and the joint region, it is known, for example from WO-A 00/20265, to produce the elastomer material of the base portion and of the joint portion from a fiber-reinforced elastomer material. Only the lip portion is not reinforced by fibers, in order that the wiping quality is not impaired. However, such fiber reinforcement has the disadvantage that the articulating properties of the joint portion are impaired, since the material as a whole is stiffened by the fiber component.
In order to avoid the lip portion of a wiper blade being permanently deformed, it is known from JP 57077241 to insert a fabric portion along the central axis of the wiping rubber. The fabric strip has a higher tensile strength that the elastomer material and shows outstanding resistance to deformations, so that, even when the wiper blade is not actuated for a long time, permanent deformation of the wiping lip is avoided. A disadvantage, however, is that the positioning of the fabric portion such as that disclosed in JP 57077241 is extremely difficult.